1. Field of the Invention
The present invention relates to disc drives and optical disc drives, and in particular, to disc drives and optical disc drives for loading and unloading discs and for writing and reading information signal to and from such discs.
2. Description of the Related Art
Conventionally, a disc drive is used in which a disc-like recording medium such as an optical disc, magneto-optical disc or magnetic disc is used as the recording medium.
The disc drives of this type include an optical disc drive in which an optical disc is used as the recording medium. In the optical disc drive, there are installed on a common base a disc rotation driver to drive the rotation of an optical disc and an optical pickup to scan, by a light beam, a signal recording area on the optical disc being rotated by the disc rotation driver, thereby reading an information signal recorded in the optical disc.
The base is formed from a thin metal plate, fixed to a support frame by means of supporting members each provided with a vibration-proofing elastic member, and fixed to a support pedestal by means of the support frame.
The support pedestal has movably installed thereon a disc tray which holds an optical disc and carries it into and out of the optical disc drive body in which the support pedestal is housed. The disc tray is supported on the support pedestal to be movable horizontally between a first position where the optical disc is projected out of the optical disc drive body and a second position where the optical disc is placed opposite to the disc rotation driving mechanism and loaded on a disc table of the disc rotation driving mechanism. The second position is a reading position.
The support frame on which the base is installed is pivoted in a direction in which the disc table of the disc rotation driving mechanism is moved towards and away from the optical disc held in the disc tray as the disc tray is moved into and out of the optical disc drive body.
In the optical disc drive constructed as in the above, as the disc tray holding an optical disc therein is moved by a tray moving mechanism from the first position towards the second position, the support frame pivots the disc table towards the optical disc held in the disc tray. When the disc tray arrives at the second position, the disc table is projected into the disc tray, the disc tray is a little levitated and the optical disc held in the disc tray is loaded on the disc table. When the optical disc is loaded onto the disc table, a clamping member provided at the optical disc drive body to be opposite to the disc table is pressed to the optical disc, so that the optical disc will be rotatable along with the disc table.
After the optical disc has become rotatable along with the disc table, the disc rotation driving mechanism is driven to move the optical pickup between the inner and outer circumferences of the optical disc being rotated along with the disc table. A signal recording area on the optical disc is scanned by a light beam emitted from the optical pickup to read an information signal recorded in the optical disc.
In the conventional disc drive, however, since the optical pickup is moved between the inner and outer circumferences of an optical disc when reading the optical disc, the weight balance of the base is varied with the movement of the optical pickup. Among others, in case the base on which the optical pickup is installed is made from a metal plate, the base will be deflected depending upon a moved position of the optical pickup and there will take place a skew with which a light beam will not be irradiated perpendicularly to a signal recording surface on the optical disc, with a result that no information signal can be read accurately. Especially, in an optical disc drive with a large and heavy optical pickup having a plurality of light sources and a plurality of photo-detectors provided therein, the base will be deflected considerably. Further, even with a little skew, no correct read of information signal can be made from an optical disc having image information, etc. recorded therein with a high density.
In an optical disc drive, in which the base is supported by supporting members each provided with an elastic member, when the weight balance of the base is changed, the weight applied to each supporting member varies, the supporting members are elastically deformed differently one from another, so that the base cannot be supported horizontally relative to a reference plane. If the base cannot be kept horizontal in an optical disc drive in which when the base is pivoted as the disc tray is pivoted, an optical disc is loaded onto the disc table, the disc tray will collide with the disc table, so that the optical disc cannot be loaded smoothly onto the disc table.
Also in a disc drive for any disc-like recording medium other than the optical disc, if the base on which the disc rotating mechanism and write and/or read head are installed is deflected as caused by the movement of the write and/or read head and thus deformed, the write and/or read head will not be able to correctly scan a recording track on the disc-like recording medium and thus to write and/or read any information signal with good writing and reading characteristics.
To prevent the base from being deflected due to a weight imbalance caused by the movement of the optical pickup and write and/or read head, it has been proposed to use a base formed from a thick metal plate which can assure a sufficient strength of the base. However, to form a base from such a thick metal plate by pressing or the like, a large force is needed. During production of a base from such a thick metal plate, the large pressure applied will cause a large internal stress in the metal plate. The internal stress will make it difficult to make the base highly flat.
Still needed in the field, therefore, is a disc drive and an optical disc drive that provides for accurate writing and reading of information signals to and from a disc loaded therein by maintaining the horizontal balance of its base despite the weight shift caused by a movement of an optical pickup and a writing and/or reading means. In addition, the disc drives and the optical disc drives should provide for smooth loading and unloading of a disc. The disc drives and the optical disc drives should have a highly flat base and should also be easily manufactured.